internet infrastructure

INTERNET  INFRASTRUCTURE

 The Internet backbone is made up of many large networks which interconnect with each other. These large networks are known as Network Service Providers or NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet, SprintNet, PSINet, as well as others. These networks peer with each other to exchange packet traffic. Each NSP is required to connect to three Network Access Points or NAPs. At the NAPs, packet traffic may jump from one NSP's backbone to another NSP's backbone. NSPs also interconnect at Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as the NAPs but are privately owned. NAPs were the original Internet interconnect points. Both NAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs also sell bandwidth to smaller networks, such as ISPs and smaller bandwidth providers.

INTERNET PROTOCOL (IP)

Unlike TCP, IP is an unreliable, connectionless protocol. IP doesn't care whether a packet gets to it's destination or not. Nor does IP know about connections and port numbers. IP's job is too send and route packets to other computers. IP packets are independent entities and may arrive out of order or not at all. It is TCP's job to make sure packets arrive and are in the correct order. About the only thing IP has in common with TCP is the way it receives data and adds it's own IP header information to the TCP data.  The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the internet. Each computer (known as a host) on the Internet has at least one  IP address  that uniquely identifies it from all other computers on the Internet.

When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet  is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighbourhood or domain. That gateway then forwards the packet directly to the computer whose address is specified.

IP add  consists of 2 part:

1.      Identifying the network

2.      Identifying the node/host

Class of addresses determines which part belongs to the network add & which part belongs to node. All nodes on a given network share the same network prefix but must have a unique host number

Class A network

Binary add start with 0 therefore decimal number can be anywhere from 1 to 126. The first 8 bits (the first octet) identify the network and the remaining 24 bits indicate the host within the network. For example 102.168.212.226

Class B network

Binary add start with 10 = decimal number can be anywhere from 128 to 191 . The number 127 is reserved for loopback and is used for internal testing on the local machine). The first 16 bits (first 2 octet) = identify the network & the remaining 16 bit indicate the host for example 168.212.226.204 

Class C network

Binary add start with 110 = decimal number can be anywhere from 192 to 223. The first 24 bits (first 3 octets) = identify the network for example 200.168.212.226

Class D network

Binary add start with 1110 = decimal number can be anywhere from 224 to 239. Used to support multicasting.

Class E network

Binary add start with 1111 = decimal number can be anywhere from 240 to 225. Used for experimentation, never been documented or utilized in a standard way.

 DOMAIN NAME SYSTEM (DNS)

Definition: The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites. DNS implements a distributed database to store this name and address information for all public hosts on the Internet. DNS assumes IP addresses do not change (are statically assigned rather than dynamically assigned).

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed and fault tolerant and has helped avoid the need for a single central register to be continually consulted and updated. Additionally, the responsibility for maintaining and updating the master record for the domains is spread among many domain name registrars, who compete for the end-user's, domain-owner's, business. Domains can be moved from registrar to registrar at any time.

INTERNET SERVICE PROVIDER

An Internet service provider (ISP) is an organization that provides access to the internet. Short for Internet Service Provider, it refers to a company that provides Internet services, including personal and business access to the internet. For a monthly fee, the service provider usually provides a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and and USENET ,send and receive e-mail. For broadband access you typically receive the broadband modem hardware or pay a monthly fee for this equipment that is added to your ISP account billing.

Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. An upstream ISP usually has a larger network than the contracting ISP and/or is able to provide the contracting ISP with access to parts of the Internet the contracting ISP by itself has no access to

Application Protocols: HTTP and the World Wide Web

One of the most commonly used services on the Internet is the World Wide Web (WWW). The application protocol that makes the web work is Hypertext Transfer Protocol or HTTP. Do not confuse this with the Hypertext Markup Language (HTML). HTML is the language used to write web pages. HTTP is the protocol that web browsers and web servers use to communicate with each other over the Internet. It is an application level protocol because it sits on top of the TCP layer in the protocol stack and is used by specific applications to talk to one another. In this case the applications are web browsers and web servers.

HTTP is a connectionless text based protocol. Clients (web browsers) send requests to web servers for web elements such as web pages and images. After the request is serviced by a server, the connection between client and server across the Internet is disconnected. A new connection must be made for each request. Most protocols are connection oriented. This means that the two computers communicating with each other keep the connection open over the Internet.

Application Protocols: SMTP and Electronic Mail

Another commonly used Internet service is electronic mail. E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP. SMTP is also a text based protocol, but unlike HTTP, SMTP is connection oriented. SMTP is also more complicated than HTTP. There are many more commands and considerations in SMTP than there are in HTTP.

Transmission Control Protocol

Under the application layer in the protocol stack is the TCP layer. When applications open a connection to another computer on the Internet, the messages they send (using a specific application layer protocol) get passed down the stack to the TCP layer. TCP is responsible for routing application protocols to the correct application on the destination computer. To accomplish this, port numbers are used. Ports can be thought of as separate channels on each computer. For example, you can surf the web while reading e-mail. This is because these two applications (the web browser and the mail client) used different port numbers. When a packet arrives at a computer and makes its way up the protocol stack, the TCP layer decides which application receives the packet based on a port number.

TCP works like this:

• When the TCP layer receives the application layer protocol data from above, it segments it into manageable 'chunks' and then adds a TCP header with specific TCP information to each 'chunk'. The information contained in the TCP header includes the port number of the application the data needs to be sent to.
• When the TCP layer receives a packet from the IP layer below it, the TCP layer strips the TCP header data from the packet, does some data reconstruction if necessary, and then sends the data to the correct application using the port number taken from the TCP header.

Unbounded media/unguided media

media doesn't use any physical connectors between the two devices communicating. this is media transport electromagnetic wave withhout physical conductor. signal are broadcasting through air or water and therefore availble to anyone who has a device capable of receiving them. usually the transmission is send through the atmosphere but sometimes it can be just across the rule.

terrestrial microwave

microwaves are radio waves with wavelengths ranging from as long as one meter to as one milimetre, or equivalently, with frenquencies between 300 MHz (0.3 GHz.). require line-sight transmission and reception equipment. towers on hills or mountains. the signal transmit one way direction at a time.

 there has 2 types of antennas:
        1. Parabolic dish
        2. Horn
1. Parabolic dish

A parabolic reflector (or dish or mirror) is a reflective device used to collect or project energy such as light,sound, or radio waves. its shape is that of a cicular paraboloid, that is, the surface generated by a parabola revolving around its axis. the parabolic reflector transforms an incoming plane wave traveling along the axis into a spherical wave converging toward the focus. Based on geometry of parabola.

2. Horn
it looks like gigantic scoop outgoing transmission are broadcast up a stem & deflected outward in a series of narrow parallel beams by the scooped shape of the horn.

 

3. Satellite
A satellite dish is a dish-shaped types of parabolic antenna designed to receive mircrowaves from communications satellites, which transmit data transmissions or broadcasts, such as satellite television. that satellite is super tall antenne and repeater. single bounce.
capability- any location on earth no matter how remote. it is high quality communication without requiring a huge investment in ground-based infrastructure. same speed as the eart.
Geosynchronous satellite - orbit speed is based on distance from the planet.
minimum 3 satellite  to provide full global transmissions. transmission from earth to satellite  is uplink however transmission from the satellite to earth is downlink.

principle of operation- the parabolic shape of a dish reflects the signal to the dish's focal point. this feedhorn is essentially the front-end of a waveguide that the signal at or near the focal point and 'conducts' them to a low-noise block downconverter or LNB.

4. WI-FI
wi-fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed internet connections. the WI-FI Alliance defines WI-FI as any " wireless local area network (WLAN) products that are based on the institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards.

A device that can use Wi-Fi (such as a personal computer, video game console, smartphone, tablet, or digital audio player) can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Hotspot coverage can comprise an area as small as a single room with walls that block radio waves or as large as many square miles — this is achieved by using multiple overlapping access points.

Radio Frequancy
Radio frequency (RF) is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist (see mechanical filter and RF MEMS). Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies. The energy in an RF current can radiate off a conductor into space as electromagnetic waves (radio waves); this is the basis of radio technology.

CABLING

what is cabling ?

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. The types of cable chosen for a network is related to the network's topology, protocol, and size.  

types of cable;

unshielded twisted pair (UTP) cable.

shielded twisted pair (STP) cable .

coaxial cable .

fiber optic cable. 

Wireless LANs.

cable installation guides.

twisted pair cabling comes in two varieties: shielded and unshielded. unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks unshielded twited pair (UTP) Cable;

The cable has four pairs of wires inside the jacket. each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other eletrical devices.

categories of unshielded twisted pairs

types use 

category 1 voice only (telephone wire)

category 2 data to 4 Mbps (local Talk)

category 3 data to 10 Mbps (Ethernet)

category 4 data to 20 Mbps (16 Mbps Token Ring)

category 5 data to 100 Mbps (Fast Ethernet)

the standard connector for unshielded twisted pair cabling is an RJ-45 connector.

RJ= Registered Jack.

A disadvantage  of UTP is that it may be susceptible to radio and electrical frequency interference.

shielded twisted pair (STP) cable

STP is a types of cable consists of two individual wires wrapped in a foil shielding to help provide a more reliable data communication.

suitable for environments with electrical interference;

however, the extra shielding can make the cable quite bulky.

often used on networks using Token Ring topology.

co-xial cable

Coaxial cabling has a single copper conductor at its center. 

A plastic layer provides insulation between the center conductor and a braided metal shield.The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Coaxial Cable Connectors.

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman  (BNC) connector.

Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator.

Week 6:

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer^[ or biological network. Network topologies may be physical or logical.Physical topology refers to the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.

There are basic categories two of network topologies;

Physical topology:

                Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that Logical topology :

                the mapping of the flow of data between the nodes in the network determines the logical topology of the network etermines the physical topology of the network.

The study of network topology recognizes eight basic topologies:^[

Point-to-point;

The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law.

Bus network topology ;

Topologi "linear bus" terdiri daripada suatu kabel utama dengan suatu penamat (terminator) dikedua-dua hujungnya. Semua nod (seperti komputer pelayan, stesyen kerja dan peranti lain) disambung kepada kabel linear ini. Contoh rangkaian yang menggunakan topologi Linear Bus ini ialah Ethernet dan LocalTalk.

Star network topology ;

In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure.

Advantages

v  Easy to install, and wire.

v  Easy to add new workstations

v  No disruptions to the network when connecting or removing devices.

v  Any non-centralised failure will have very little effect on the network

v  Easy to detect faults and to remove parts.

v  Centralized control

v  Centralized network/hub monitoring

Disadvantages

v  Requires more cable length than a linear topology.

v  If the hub or concentrator fails, nodes attached are disabled.

More expensive than linear bus topologies because of the cost of the concentrators

Ring network topology;

A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

Fully connected mesh topology;

Partially connected mesh topology;

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Tree network topology

Advantage

v  Point-to-point wiring for individual segments.

Disadvantages

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.

Hybrid;

Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network.

Daisy chain;

Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.

week 5

what is networking ?

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. 

Two very common types of networks include;

·         local Area Network (LAN) 

           Wide Area Network (WAN)

You may also see references to a Metropolitan Area Networks (MAN), a Wireless LAN (WLAN), or a Wireless WAN (WWAN).

 Local Area Network

A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Computers connected to a network are broadly categorized as servers or workstations.

Workstations are called such because they typically do have a human user which interacts with the network through them. Workstations were traditionally considered a desktop, consisting of a computer, keyboard, display, and mouse, or a laptop, with integrated keyboard, display, and touchpad. With the advent of the tablet computer, and the touch screen devices such as iPad and iPhone, our definition of workstation is quickly evolving to include those devices, because of their ability to interact with the network and utilize network services. 

Wide Area Network

Wide Area Networks (WANs) connect networks in larger geographic areas, such as Florida, the United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of global network.

sing a WAN, schools in Florida can communicate with places like Tokyo in a matter of seconds, without paying enormous phone bills. Two users a half-world apart with workstations equipped with microphones and a webcams might teleconference in real time. A WAN is complicated. It uses multiplexers, bridges, and routers to connect local and metropolitan networks to global communications networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN.

Metropolitan area network

A metropolitan  area network (MAN) is a computer network that usually spans a city or a large campus. A MAN usually inter connects a number of local area network (LAN) using a high-capacity backbone technology, such as fiber-optical links,and provides up-link services to wide area network(or WAN) and the internet.

Personal area network

 A personal area network (PAN) is a computer network used for communication  among computerized devices, including telephones  and personal digital assistans. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the internet(an uplink). 
A wireless personal area network (WPAN) is a PAN carried over wireless network technologies such as irDA, Bluetooth,Wireless USB, zigBee, or even Body carried over wired computer buses such as USB and FireWire.
A wireless personal area network (WPAN) is a personal area network - a network for interconnecting devices centered around an individual person's workspace - in which the connections are wireless. Wireless PAN is based on the standard IEEE 802.15. The three kinds of wireless technologies used for WPAN are Bluetooth,infrared data Association, and Wi-Fi.

Bluetooth

Bluetooth uses short-range radio waves over distances up to approximately 10 metres. For example, Bluetooth devices such as a keyboards, pointing devices, audio head sets, printers may connect to personal digital assistants (PDAs), cell phones,or computers wirelessly.

A Bluetooth PAN is also called a piconet(combination of the prefix "pico," meaning very small or one trillionth, and network), and is composed of up to 8 active devices in a master-slave relationship (a very large number of devices can be connected in "parked" mode). The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. A piconet typically has a range of 10 metres (33 ft), although ranges of up to 100 metres (330 ft) can be reached under ideal circumstances.